U.S. patent application number 10/125558 was filed with the patent office on 2002-10-31 for seal ring.
This patent application is currently assigned to DAIKIN INDUSTRIES, LTD.. Invention is credited to Asano, Michio, Sukegawa, Masamichi, Yanagiguchi, Tomihiko.
Application Number | 20020158424 10/125558 |
Document ID | / |
Family ID | 17874078 |
Filed Date | 2002-10-31 |
United States Patent
Application |
20020158424 |
Kind Code |
A1 |
Yanagiguchi, Tomihiko ; et
al. |
October 31, 2002 |
Seal ring
Abstract
A seal ring comprising 40 to 94% by weight of a
polytetrafluoroethylene powder, 3 to 30% by weight of a heat
resistant aromatic polyoxybenzoyl ester resin powder and 3 to 30%
by weight of a graphite powder. A stable sealing effect can be
obtained for a long period of time since a deformation of the seal
ring is small for the use even under a high pressure and an
abrasion of an opposite material can be inhibited even if the
opposite material is a soft metal. Further a frictional force is
small, and a change in a sliding torque is small. Therefore the
seal ring is suitable as a seal ring for a power steering where
operability and response of the sealing device can be enhanced and
also as a seal ring for an automatic transmission which slides at
high revolutions and as a seal ring for a shock absorber which is
required to have a sealing property under reciprocating sliding
environment.
Inventors: |
Yanagiguchi, Tomihiko;
(Osaka, JP) ; Sukegawa, Masamichi; (Osaka, JP)
; Asano, Michio; (Osaka, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
WASHINGTON
DC
20037
US
|
Assignee: |
DAIKIN INDUSTRIES, LTD.
|
Family ID: |
17874078 |
Appl. No.: |
10/125558 |
Filed: |
April 19, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10125558 |
Apr 19, 2002 |
|
|
|
PCT/JP00/07274 |
Oct 19, 2000 |
|
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Current U.S.
Class: |
277/650 |
Current CPC
Class: |
F16J 15/102 20130101;
F16F 9/368 20130101 |
Class at
Publication: |
277/650 |
International
Class: |
F16J 015/08 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 21, 1999 |
JP |
299550/1999 |
Claims
What is claimed is:
1. A seal ring comprising 40 to 94% by weight of a
polytetrafluoroethylene powder, 3 to 30% by weight of a heat
resistant aromatic polyoxybenzoyl ester resin powder and 3 to 30%
by weight of a graphite powder.
2. The seal ring of claim 1, wherein the polytetrafluoroethylene
powder is a powder of polytetrafluoroethylene modified with a
monomer copolymerizable with tetrafluoroethylene.
3. The seal ring of claim 1, wherein the graphite powder is a
natural graphite powder.
4. The seal ring of claim 1 which is used for a valve device of a
power steering of automobiles.
5. The seal ring of claim 3, in which when a sliding cycle is
applied on the seal ring under the following conditions, breakage
of the seal ring does not occur at the 200,000th cycle, a sliding
torque during the period of time of from the 10,000th cycle to the
200,000th cycle is within the range of not less than 75% of the
maximum sliding torque in that period, and an abraded depth of an
opposite material after 200,000 cycles is not more than 15 .mu.m.
Test equipment: Test equipment for evaluating durability of a seal
ring which conforms with a rack & pinion type power steering
device Oil pressure: 12 MPa Oil temperature: 120.degree. C. Kind of
oil: Power steering fluid Cycle: One cycle consists of a normal
rotation at 95 rpm for 2 seconds and a reverse rotation at 95 rpm
for 2 seconds Opposite material: Aluminum die cast (JIS H5302) Seal
ring-mounting material: Carbon steel (JIS G4051) Seal ring: 36.4 mm
of outer diameter, 1.5 mm of width, 1.88 mm of height
6. The seal ring of claim 1, which is used for a valve device of a
power steering of large-sized car operable at an oil pressure of
not less than 12 MPa, in which when a sliding cycle is applied on
the seal ring under the following conditions, breakage of the seal
ring does not occur at the 200,000th cycle, a sliding torque within
the period of 200,000 cycles without the period of initial unstable
sliding torque is not less than 75% of the maximum sliding torque
in that period of 200,000 cycles, and during the period of 200,000
cycles without the period of initial unstable sliding torque, a
ratio Tmax15/Tmax12 of the maximum sliding torque Tmax15 at an oil
pressure of 15 MPa to the maximum sliding torque Tmax12 at an oil
pressure of 12 MPa is less than 1.5. Test equipment: Test equipment
for evaluating durability of a seal ring which conforms with a rack
& pinion type power steering device Oil pressure: 12 MPa and 15
MPa Oil temperature: 120.degree. C. Kind of oil: Power steering
fluid Cycle: One cycle consists of a normal rotation at 95 rpm for
2 seconds and a reverse rotation at 95 rpm for 2 seconds Opposite
material: Carbon steel (JIS G3445) Seal ring-mounting material:
Carbon steel (JIS G4051) Seal ring: 36.4 mm of outer diameter, 1.5
mm of width, 1.88 mm of height
7. The seal ring of claim 1, which is used for an automatic
transmission, in which when a rotation slide is applied on the seal
ring under the following conditions, breakage of the seal ring does
not occur in 500 hours and an abraded depth of an opposite material
500 hours after applying the rotation slide is not more than 10
.mu.m. Test equipment: Test equipment for evaluating durability of
a seal ring which conforms with an automatic transmission device
Oil pressure: 2 MPa Oil temperature: 120.degree. C. Kind of oil:
Automatic transmission fluid Number of rotations: 8,000 rpm
Opposite material: Aluminum die cast (JIS H5302) Seal ring-mounting
material: Cast iron (JIS G5501) Seal ring: 50 mm of outer diameter,
2 mm of width, 2 mm of height
8. The seal ring of claim 1, which is used for a shock absorber, in
which when reciprocating slide strokes are applied on the seal ring
under the following conditions, breakage of the seal ring does not
occur at the 5,000,000th stroke, the maximum slide resistance Fmax
within the period of 5,000,000 strokes without the period of
initial unstable slide resistance is less than 1.5 times the
minimum slide resistance Fmin during that period of 5,000,000
strokes, and an amount of oil leakage after 5,000,000 strokes is
not more than 15 ml. Test equipment: Test equipment for evaluating
durability of a seal ring which conforms with a shock absorber
device Oil pressure: 10 MPa Oil temperature: 100.degree. C . Kind
of oil: Shock absorber oil Length of stroke: 60 mm Vibration
frequency to be applied: 3 Hz Opposite material: Carbon steel (JIS
G4051) Seal ring-mounting material: Cast iron (JIS G5501) Seal
ring: 28.5 mm of outer diameter, 7.4 mm of width, 0.8 mm of height
(diameter of piston: 25 mm)
9. The seal ring of claim 4, in which when a sliding cycle is
applied on the seal ring under the following conditions, breakage
of the seal ring does not occur at the 200,000th cycle, a sliding
torque during the period of time of from the 10,000th cycle to the
200,000th cycle is within the range of not less than 75% of the
maximum sliding torque in that period, and an abraded depth of an
opposite material after 200,000 cycles is not more than 15 .mu.m.
Test equipment: Test equipment for evaluating durability of a seal
ring which conforms with a rack & pinion type power steering
device Oil pressure: 12 MPa Oil temperature: 120.degree. C. Kind of
oil: Power steering fluid Cycle: One cycle consists of a normal
rotation at 95 rpm for 2 seconds and a reverse rotation at 95 rpm
for 2 seconds Opposite material: Aluminum die cast (JIS H5302) Seal
ring-mounting material: Carbon steel (JIS G4051) Seal ring: 36.4 mm
of outer diameter, 1.5 mm of width, 1.88 mm of height
10. The seal ring of claim 2, which is used for a valve device of a
power steering of large-sized car operable at an oil pressure of
not less than 12 MPa, in which when a sliding cycle is applied on
the seal ring under the following conditions, breakage of the seal
ring does not occur at the 200,000th cycle, a sliding torque within
the period of 200,000 cycles without the period of initial unstable
sliding torque is not less than 75% of the maximum sliding torque
in that period of 200,000 cycles, and during the period of 200,000
cycles without initial unstable sliding torque, a ratio
Tmax15/Tmax12 of the maximum sliding torque Tmax15 at an oil
pressure of 15 MPa to the maximum sliding torque Tmax12 at an oil
pressure of 12 MPa is less than 1.5. Test equipment: Test equipment
for evaluating durability of a seal ring which conforms with a rack
& pinion type power steering device Oil pressure: 12 MPa and 15
MPa Oil temperature: 120.degree. C. Kind of oil: Power steering
fluid Cycle: One cycle consists of a normal rotation at 95 rpm for
2 seconds and a reverse rotation at 95 rpm for 2 seconds Opposite
material: Carbon steel (JIS G3445) Seal ring-mounting material:
Carbon steel (JIS G4051) Seal ring: 36.4 mm of outer diameter, 1.5
mm of width, 1.88 mm of height
11. The seal ring of claim 2, which is used for an automatic
transmission, in which when a rotation slide is applied on the seal
ring under the following conditions, breakage of the seal ring does
not occur in 500 hours and an abraded depth of the opposite
material 500 hours after applying the rotation slide is not more
than 10 .mu.m. Test equipment: Test equipment for evaluating
durability of a seal ring which conforms with an automatic
transmission device Oil pressure: 2 MPa Oil temperature:
120.degree. C. Kind of oil: Automatic transmission fluid Number of
rotations: 8,000 rpm Opposite material: Aluminum die cast (JIS
H5302) Seal ring-mounting material: Cast iron (JIS G5501) Seal
ring: 50 mm of outer diameter, 2 mm of width, 2 mm of height
12. The seal ring of claim 2, which is used for a shock absorber,
in which when reciprocating slide strokes are applied on the seal
ring under the following conditions, breakage of the seal ring does
not occur at the 5,000,000th stroke, the maximum slide resistance
Fmax within the period of 5,000,000 strokes without the period of
initial unstable slide resistance is less than 1.5 times the
minimum slide resistance Fmin during that period of 5,000,000
strokes, and an amount of oil leakage after 5,000,000 strokes is
not more than 15 ml. Test equipment: Test equipment for evaluating
durability of a seal ring which conforms with a shock absorber
device Oil pressure: 10 MPa Oil temperature: 100.degree. C. Kind of
oil: Shock absorber oil Length of stroke: 60 mm Vibration frequency
to be applied: 3 Hz Opposite material: Carbon steel (JIS G4051)
Seal ring-mounting material: Cast iron (JIS G5501) Seal ring: 28.5
mm of outer diameter, 7.4 mm of width, 0.8 mm of height (diameter
of piston: 25 mm)
13. The seal ring of claim 3, which is used for a valve device of a
power steering of large-sized car operable at an oil pressure of
not less than 12 MPa, in which when a sliding cycle is applied on
the seal ring under the following conditions, breakage of the seal
ring does not occur at the 200,000th cycle, a sliding torque within
the period of 200,000 cycles without the period of initial unstable
sliding torque is not less than 75% of the maximum sliding torque
in that period of 200,000 cycles, and during the period of 200,000
cycles without the period of initial unstable sliding torque, a
ratio Tmax15/Tmax12 of the maximum sliding torque Tmax15 at an oil
pressure of 15 MPa to the maximum sliding torque Tmax12 at an oil
pressure of 12 MPa is less than 1.5. Test equipment: Test equipment
for evaluating durability of a seal ring which conforms with a rack
& pinion type power steering device Oil pressure: 12 MPa and 15
MPa Oil temperature: 120.degree. C. Kind of oil: Power steering
fluid Cycle: One cycle consists of a normal rotation at 95 rpm for
2 seconds and a reverse rotation at 95 rpm for 2 seconds Opposite
material: Carbon steel (JIS G3445) Seal ring-mounting material:
Carbon steel (JIS G4051) Seal ring: 36.4 mm of outer diameter, 1.5
mm of width, 1.88 mm of height
14. The seal ring of claim 3, which is used for an automatic
transmission, in which when a rotation slide is applied on the seal
ring under the following conditions, breakage of the seal ring does
not occur in 500 hours and an abraded depth of an opposite material
500 hours after applying the rotation slide is not more than 10
.mu.m. Test equipment: Test equipment for evaluating durability of
a seal ring which conforms with an automatic transmission device
Oil pressure: 2 MPa Oil temperature: 120.degree. C. Kind of oil:
Automatic transmission fluid Number of rotations: 8,000 rpm
Opposite material: Aluminum die cast (JIS H5302) Seal ring-mounting
material: Cast iron (JIS G5501) Seal ring: 50 mm of outer diameter,
2 mm of width, 2 mm of height
15. The seal ring of claim 3, which is used for a shock absorber,
in which when reciprocating slide strokes are applied on the seal
ring under the following conditions, breakage of the seal ring does
not occur at the 5,000,000th stroke, the maximum slide resistance
Fmax within the period of 5,000,000 strokes without the period of
initial unstable slide resistance is less than 1.5 times the
minimum slide resistance Fmin during that period of 5,000,000
strokes, and an amount of oil leakage after 5,000,000 strokes is
not more than 15 ml. Test equipment: Test equipment for evaluating
durability of a seal ring which conforms with a shock absorber
device Oil pressure: 10 MPa Oil temperature: 100.degree. C. Kind of
oil: Shock absorber oil Length of stroke: 60 mm Vibration frequency
to be applied: 3 Hz Opposite material: Carbon steel (JIS G4051)
Seal ring-mounting material: Cast iron (JIS G5501) Seal ring: 28.5
mm of outer diameter, 7.4 mm of width, 0.8 mm of height (diameter
of piston: 25 mm)
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a continuation-in-part of PCT international
application No. PCT/JP00/07274 filed on Oct. 19, 2000 pending.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a seal ring, particularly a
seal ring which realizes a stable sliding torque for a long period
of time from staring of use. The seal ring of the present invention
can be suitably used particularly as a seal ring of a valve device
of a power steering of passenger cars and large-sized cars. Also
since the seal ring of the present invention can realize an
abrasion resistance and a stable friction resistance to an opposite
material for a long period of time from starting of its use, it can
be suitably used as a seal ring for an automatic transmission and
also as a seal ring for a shock absorber.
[0003] To a polytetrafluoroethylene (PTFE) powder (granular resin
powder) is added frequently an organic filler such as a polyimide
resin powder or an inorganic filler such as a carbon fiber, bronze
powder or graphite powder in order to make up for defects such as
an insufficient strength of a molded article obtained therefrom
while making the best use of its properties such as non-tackiness,
sliding property and heat resistance. Thus there have been proposed
PTFE compositions prepared in combination with various fillers
according to purpose and application.
[0004] Seal rings are used for such an application as shown, for
example, in a diagrammatic cross-sectional view of FIG. 1. Namely,
the seal ring 1 is a ring-like member which is put between the two
members (housing 2 and seal ring set body 3) undergoing relative
motion at a rotating or sliding portion and is used to seal oil 4.
In FIG. 1, the seal ring 1 is wound over the seal ring set body 3
and forms a sliding surface to the housing 2. During the use, as
shown in FIG. 2, the seal ring set body 3 rotates on the housing 2,
and a relatively high pressure is applied on the seal ring from the
oil 4. Further when normal and reverse rotations are repeated,
there is a case where a sliding torque fluctuates markedly during
the use and an end of the seal ring 1 is abraded as a result of a
long term use, thereby causing an extruded portion 5 (FIG. 3). Also
when the housing 2 is made of a soft metal such as aluminum, there
is a case where the housing 2 is abraded and a concave portion 6 is
produced (FIG. 4) and leaking of the oil 4 occurs.
[0005] Such problems with the seal ring are important problems to
be solved particularly in the devices of automobile such as a power
steering in which importance is placed on feeling and safety during
driving.
[0006] Even in case where the pressure from the oil 4 is relatively
low, when the seal ring set body 3 is rotated on the housing 2 at a
high speed and the housing 2 is made of a soft metal such as
aluminum, as a result of a long term use, there is a case where the
housing 2 is abraded and also a concave portion 6 is produced,
thereby causing leakage of the oil 4.
[0007] Such problems with the seal ring are important problems to
be solved particularly in the devices of automobile such as an
automatic transmission in which importance is attached to safety
during driving.
[0008] Further when the seal ring 1 is used put between the two
members, namely the piston 7 and the cylinder 8 undergoing relative
motion as shown in the diagrammatic cross-sectional view of FIG. 5
and when the piston 7 undergoes a reciprocating motion against the
cylinder 8 repeatedly while the oil 4 is sealed with the seal ring
1, there is a case where a friction resistance (sliding resistance)
produced on the sliding surface between the seal ring 1 and the
cylinder 8 during the use fluctuates markedly, an end of the seal
ring 1 is abraded as a result of long term use as shown in FIG. 6,
and even when the cylinder 8 is made of a relatively hard carbon
steel, the cylinder 8 is abraded and a concave portion 9 is
produced, thereby causing leaking of the oil 4.
[0009] Such problems with the seal ring are important problems to
be solved particularly in the devices such as a shock absorber in
which importance is attached to safety during the operation.
[0010] Examples of known PTFE compositions which have been proposed
as the PTFE composition for a seal ring required to have the
above-mentioned properties are:
[0011] (1) PTFE powder/polyimide (PI) powder/carbon fiber
(JP-A-9-208929, etc.)
[0012] (2) PTFE powder/heat resistant aromatic polyoxybenzoyl ester
resin powder/carbon fiber (JP-B-1-13494, JP-A-11-21408), and
[0013] (3) PTFE powder/graphite powder/carbon fiber
(JP-A-5-239440).
[0014] However particularly under a high oil pressure of not less
than 8 MPa, breakage of a seal ring and abrasion of an opposite
material (housing) occur in a relatively short period of time, and
it has been considered that conventional PTFE compositions have a
certain limit in durability.
[0015] Also under a sliding environment where the number of
revolutions is as high as not less than 7,000 rpm, abrasion of an
opposite material occurs in a relatively short period of time, and
it has been considered that conventional PTFE compositions have a
certain limit in durability.
[0016] Further in an environment where a reciprocating slide is
repeated under a high oil pressure of not less than 8 MPa, breakage
of a seal ring and abrasion of an opposite material occur in a
relatively short period of time, and it has been considered
similarly that conventional PTFE compositions have a certain limit
in durability.
[0017] An object of the present invention is to provide a seal ring
which undergoes a small change in a sliding torque, is free from
breakage and assures a small amount of abrasion of the opposite
material during the long term use even under environments of a high
oil pressure, the large number of revolutions and a high speed
reciprocating motion. The seal ring has properties breaking through
limits of the properties of conventional seal rings.
SUMMARY OF THE INVENTION
[0018] Namely, the present invention relates to a seal ring
comprising 40 to 94% by weight of a PTFE powder, 3 to 30% by weight
of a heat resistant aromatic polyoxybenzoyl ester resin powder and
3 to 30% by weight of a graphite powder.
[0019] It is preferable that the PTFE powder is a modified PTFE
powder and the graphite powder is a natural graphite powder.
[0020] The seal ring of the present invention can exhibit its
properties particularly as a seal ring for a valve device of a
power steering of automobiles.
[0021] The valve device of a power steering of automobiles is
composed of the housing 2, the seal ring set body 3 and the seal
ring 1 which is made of a resin and is present between the housing
2 and the seal ring set body 3 for sealing of oil 4 as shown in
FIG. 1, and the seal ring 1 is characterized by comprising a PTFE
resin composition comprising 40 to 94% by weight of a PTFE powder,
3 to 30% by weight of a heat resistant aromatic polyoxybenzoyl
ester resin powder and 3 to 30% by weight of a graphite powder.
[0022] Also the present invention relates to a seal ring in which
when a sliding cycle is applied on the seal ring under the
following Condition 1 which is a normal test condition for
evaluating durability of a seal ring, breakage of the seal ring
does not occur at the 200,000th cycle, a sliding torque within the
period of 200,000 cycles without the period of initial unstable
sliding torque is not less than 75% of the maximum sliding torque
in that period of 200,000 cycles, and an abraded depth of an
opposite material after 200,000 cycles is not more than 15
.mu.m.
[0023] (Condition 1)
[0024] Test equipment: Test equipment for evaluating durability of
a seal ring which conforms with a rack & pinion type power
steering device
[0025] Oil pressure: 12 MPa
[0026] Oil temperature: 120.degree. C.
[0027] Kind of oil: Power steering fluid
[0028] Cycle: One cycle consists of a normal rotation at 95 rpm for
2 seconds and a reverse rotation at 95 rpm for 2 seconds
[0029] Opposite material: Aluminum die cast (JIS H5302)
[0030] Seal ring-mounting material: Carbon steel (JIS G4051)
[0031] Seal ring: 36.4 mm of outer diameter, 1.5 mm of width, 1.88
mm of height
[0032] In the present invention, the test for evaluating durability
of the seal ring is carried out using the seal ring having the
above-mentioned form (36.4 mm of outer diameter, 1.5 mm of width,
1.88 mm of height) which is generally used in Japan. Besides that,
there is a case where other forms are used, namely 36.2 mm of outer
diameter.times.1.25 mm of width.times.1.83 mm of height and 38.4 mm
of outer diameter.times.1.45 mm of width.times.2.00 mm of height.
Even when the seal rings having those forms are used, nearly the
same measuring results can be obtained irrespective of a difference
in the forms.
[0033] The test equipment for evaluating durability of a seal ring
has a structure conforming with a valve device (actual device) of a
power steering which is actually used on automobiles. The structure
conforming with an actual device means that the structures of a
seal ring-mounting portion and a sliding portion are the same as in
the actual device (hereinafter the same with respect to other test
equipment). As far as a rack & pinion type power steering is
used on the valve device for a power steering of automobiles, since
the devices have the same structures with respect to the seal
ring-mounting portion and the sliding portion irrespective of types
of automobiles, properties of the seal ring which are obtained in
an actual device can be obtained and evaluated using the
above-mentioned test equipment. A cross-section of the actual valve
device is shown in FIG. 5(a) of "ENGINEERING JOURNAL No. 148, pg.
92 (1995)" published by Koyo Seiko Co., Ltd.
[0034] Also the present invention relates to a seal ring for a
valve device of a power steering of a large-sized car, in which an
oil pressure of the valve device is not less than 12 MPa and the
seal ring is required to undergo a small torque change at a high
oil pressure.
[0035] When a sliding cycle is applied on such a seal ring of a
power steering of a large-sized car under the following Condition
2, breakage of the seal ring does not occur at the 200,000th cycle,
a sliding torque within the period of 200,000 cycles without the
period of initial unstable sliding torque is not less than 75% of
the maximum sliding torque in that period of 200,000 cycles, and
during the period of 200,000 cycles without the period of initial
unstable sliding torque, a ratio Tmax15/Tmax12 of the maximum
sliding torque Tmax15 at an oil pressure of 15 MPa to the maximum
sliding torque Tmax12 at an oil pressure of 12 MPa is less than
1.5.
[0036] (Condition 2)
[0037] Test equipment: Test equipment for evaluating durability of
a seal ring which conforms to a rack & pinion type power
steering device
[0038] Oil pressure: 12 MPa and 15 MPa
[0039] Oil temperature: 120.degree. C.
[0040] Kind of oil: Power steering fluid
[0041] Cycle: One cycle consists of a normal rotation at 95 rpm for
2 seconds and a reverse rotation at 95 rpm for 2 seconds
[0042] Opposite material: Carbon steel (JIS G3445)
[0043] Seal ring-mounting material: Carbon steel (JIS G4051)
[0044] Seal ring: 36.4 mm of outer diameter, 1.5 mm of width, 1.88
mm of height
[0045] Also the seal ring of the present invention is suitable as a
seal ring for an automatic transmission.
[0046] The automatic transmission device is composed of the housing
2, the seal ring set body 3 and the seal ring 1 which is made of a
resin and is present between the housing 2 and the seal ring set
body 3 for sealing of oil 4, and the seal ring 1 is characterized
by comprising a PTFE resin composition comprising 40 to 94% by
weight of a PTFE powder, 3 to 30% by weight of a heat resistant
aromatic polyoxybenzoyl ester resin powder and 3 to 30% by weight
of a graphite powder.
[0047] When a rotation slide is applied on such a seal ring for an
automatic transmission under the following Condition 3, breakage of
the seal ring does not occur in 500 hours, and an abraded depth of
an opposite material 500 hours after applying the rotation slide is
not more than 10 .mu.m.
[0048] (Condition 3)
[0049] Test equipment: Test equipment for evaluating durability of
a seal ring which conforms with an automatic transmission
device
[0050] Oil pressure: 2 MPa
[0051] Oil temperature: 120.degree. C.
[0052] Kind of oil: Automatic transmission fluid
[0053] Number of rotations: 8,000 rpm
[0054] Opposite material: Aluminum die cast (JIS H5302)
[0055] Seal ring-mounting material: Cast iron (JIS G5501)
[0056] Seal ring: 50 mm of outer diameter, 2 mm of width, 2 mm of
height
[0057] Further the seal ring of the present invention is suitable
as a seal ring for a shock absorber in which a reciprocating slide
(stroke) is applied at a high number of strokes.
[0058] The shock absorber device is composed of the cylinder 8, the
piston 7 and the seal ring 1 which is made of a resin and is
present between the cylinder 8 and the piston 7 for sealing of oil
4, and the seal ring 1 is characterized by comprising a PTFE resin
composition comprising 40 to 94% by weight of a PTFE powder, 3 to
30% by weight of a heat resistant aromatic polyoxybenzoyl ester
resin powder and 3 to 30% by weight of a graphite powder.
[0059] When the reciprocating slide strokes are applied on such a
seal ring for a shock absorber under the following Condition 4,
breakage of the seal ring does not occur at the 5,000,000th stroke,
the maximum slide resistance Fmax within the period of 5,000,000
strokes without the period of initial unstable slide resistance is
less than 1.5 times the minimum slide resistance Fmin during that
period of 5,000,000 strokes, and an amount of oil leakage after
5,000,000 strokes is not more than 15 ml.
[0060] (Condition 4)
[0061] Test equipment: Test equipment for evaluating durability of
a seal ring which conforms with a shock absorber device
[0062] Oil pressure: 10 MPa
[0063] Oil temperature: 100.degree. C.
[0064] Kind of oil: Shock absorber oil
[0065] Length of stroke: 60 mm
[0066] Vibration frequency to be applied: 3 Hz
[0067] Opposite material: Carbon steel (JIS G4051)
[0068] Seal ring-mounting material: Cast iron (JIS G5501)
[0069] Seal ring: 28.5 mm of outer diameter, 7.4 mm of width, 0.8
mm of height (diameter of piston: 25 mm)
BRIEF DESCRIPTION OF THE DRAWINGS
[0070] FIG. 1 is a partial diagrammatic cross-sectional view of the
seal ring of the present invention mounted on a power steering
device or an automatic transmission device.
[0071] FIG. 2 is a partial diagrammatic cross-sectional view
showing a usual deformation of the seal ring which arises when the
device shown in FIG. 1 is rotated.
[0072] FIG. 3 is a partial diagrammatic cross-sectional view
showing a state of damage of the seal ring which arises when the
device shown in FIG. 1 is rotated.
[0073] FIG. 4 is a partial diagrammatic cross-sectional view
showing a condition of abrasion of the opposite material (housing)
to the seal ring which arises when the device shown in FIG. 1 is
rotated.
[0074] FIG. 5 is a partial diagrammatic cross-sectional view of the
seal ring of the present invention mounted on a shock absorber
device.
[0075] FIG. 6 is a partial diagrammatic cross-sectional view
showing a condition of abrasion of the seal ring and the opposite
material (cylinder) which arises when the device shown in FIG. 5 is
subjected to reciprocating motion.
[0076] FIG. 7 is a graph showing a change in a sliding torque of
the seal ring of Example 1 used in the durability test.
[0077] FIG. 8 is a graph showing a change in a sliding torque of
the seal ring of Example 2 used in the durability test.
[0078] FIG. 9 is a graph showing a change in a sliding torque of
the seal ring of Example 3 used in the durability test.
[0079] FIG. 10 is a graph showing a change in a sliding torque of
the seal ring of Comparative Example 1 used in the durability
test.
[0080] FIG. 11 is a graph showing a change in a sliding torque of
the seal ring of Comparative Example 2 used in the durability
test.
[0081] FIG. 12 is a graph showing a change in a sliding torque of
the seal ring of Comparative Example 3 used in the durability
test.
[0082] FIG. 13 is a graph showing a change in a sliding torque of
the seal ring of Comparative Example 4 used in the durability
test.
[0083] FIG. 14 is a graph showing a change in a sliding torque at
the oil pressures of 12 MPa and 15 MPa of the seal ring of Example
4 used in the durability test.
[0084] FIG. 15 is a graph showing a change in a sliding torque at
the oil pressures of 12 MPa and 15 MPa of the seal ring of
Comparative Example 5 used in the durability test.
[0085] FIG. 16 is a graph showing a change in a sliding torque at
the oil pressures of 12 MPa and 15 MPa of the seal ring of
Comparative Example 6 used in the durability test.
[0086] FIG. 17 is a graph showing a change in a sliding torque at
the oil pressures of 12 MPa and 15 MPa of the seal ring of
Comparative Example 7 used in the durability test.
[0087] FIG. 18 is a diagrammatic plane view of a cut portion of the
seal ring of Example 5 for the automatic transmission device used
in the durability test.
DETAILED DESCRIPTION
[0088] In the present invention, the PTFE powder may be a
tetrafluoroethylene homopolymer or PTFE modified with a monomer
copolymerizable with tetrafluoroethylene, and preferred is the
modified PTFE powder from the viewpoint of excellent heat
resistance, chemical resistance and creep resistance.
[0089] Examples of the modified PTFE are, for instance, those which
are not melt-moldable and contain from 0.001 to 1% by weight of a
perfluoro vinyl ether unit represented by the formula (1):
--CF.sub.2--CF(--O--X)-- (1)
[0090] wherein X is a perfluoroalkyl group having 1 to 6 carbon
atoms or a perfluoroalkoxyalkyl group having 4 to 9 carbon
atoms.
[0091] Examples of the perfluoro vinyl ether are, for instance,
perfluoro(alkyl vinyl ethers) such as perfluoro(methyl vinyl ether)
(PMVE), perfluoro(ethyl vinyl ether) (PEVE), perfluoro(propyl vinyl
ether) (PPVE) and perfluoro(butyl vinyl ether) (PBVE).
[0092] Examples of the modified PTFE are, for instance, Teflon.RTM.
NXT-70 and Teflon.RTM. NXT-75 available from E. I. du Pont de
Nemours and Company, Teflon.RTM. TG-70-J available from Du
Pont-Mitsui Fluorochemicals Company Ltd., Dyneon.RTM. TFM PTFE
TFM-1700 and Dyneon.RTM. TF PTFE TF-1702 available from Dyneon
GmbH, and DAIKIN POLYFLON PTFE.RTM. M111 and DAIKIN POLYFLON
PTFE.RTM. M112 available from Daikin Industries, Ltd. The content
of perfluoro vinyl ether is within the range of from 0.01 to 0.50%
by weight.
[0093] The average particle size of the PTFE powder is from 10 to
120 .mu.m, preferably from 10 to 50 .mu.m.
[0094] In the present invention, for example, a powder of a resin
having a structural unit (I): 1
[0095] is preferred as the heat resistant aromatic polyoxybenzoyl
ester resin powder from the viewpoint of excellent heat resistance,
chemical resistance and abrasion resistance. In addition to the
structural unit (I), the resin powder may have the structural unit
(II) and/or (III): 2
[0096] wherein X is --O--, m is 0 or 1, n is 0 or 1. Examples of
commercially available resin powder are, for instance, SUMICA SUPER
(available from Sumitomo Chemical Company, Limited), EKONOL
(available from Carborandom Co., Ltd.), etc. It is preferable that
the average particle size is from 1 to 300 .mu.m, more preferably
from 5 to 150 .mu.m, particularly preferably from 10 to 50 .mu.m
from the viewpoint of good dispersibility of the resin powder and
excellent strength of the obtained seal ring.
[0097] The heat resistant aromatic polyoxybenzoyl ester resin
powder may be subjected to surface treatment with a silane coupling
agent or various water repelling treatments.
[0098] Examples of the graphite powder are, for instance, natural
graphite, artificial graphite, expanded graphite, graphite
fluoride, spherical carbon, carbon fluoride, graphite whisker, etc.
Particularly preferred is a natural graphite powder. It is
preferable that the average particle size of the graphite powder is
from 0.1 to 500 .mu.m, particularly preferably from 5 to 20
.mu.m.
[0099] The proportion (% by weight) of PTFE powder, heat resistant
aromatic polyoxybenzoyl ester resin powder and graphite powder is
40 to 94/3 to 30/3 to 30 (100% by weight in total), preferably 70
to 90/5 to 15/5 to 15, particularly preferably 75 to 90/5 to 15/5
to 10. If the amount of the heat resistant aromatic polyoxybenzoyl
ester resin powder is too large, inherent properties of the PTFE
are lowered, and if the amount is too small, abrasion resistance is
lowered. If the amount of the graphite powder is too large, the
opposite material made of a soft metal such as aluminum is easily
damaged, and if the amount of the graphite powder is too small,
durability is lowered.
[0100] In the present invention, only two kinds of fillers, i.e.
heat resistant aromatic polyoxybenzoyl ester resin powder and
graphite powder suffice, and so far as the intended effect of the
present invention is not lowered, other fillers may be blended.
[0101] The above-mentioned powders are mixed by usual method, and
if required, are granulated to be formed into a resin powder for
molding into a seal ring and are molded into the seal ring by
various known molding methods, for example, compression molding
method, ram extrusion molding method, isostatic molding method, hot
coining molding method, etc. In any of those molding methods, the
molded article is finally subjected to sintering. In the present
invention, the sintering temperature is from 323.degree. to
400.degree. C., preferably from 350.degree. to 385.degree. C.
[0102] The thus obtained seal ring satisfies the following
characteristics under the above-mentioned test Condition 1.
[0103] (A) Breakage of the seal ring does not occur at the
200,000th sliding cycle.
[0104] (B) A sliding torque during the period of time of from the
10,000th cycle to the 200,000th cycle is within the range of not
less than 75%, preferably not less than 80% of the maximum sliding
torque in that period.
[0105] (C) An abraded depth of the opposite material after 200,000
cycles is not more than 15 .mu.m, preferably not more than 10
.mu.m, particularly preferably not more than 5 .mu.m.
[0106] The seal ring having all of those three characteristics is
an epoch-making seal ring markedly exceeding the limit of
conventional seal rings.
[0107] With respect to large-sized cars such as trucks and special
cars such as power shovel and bulldozer, a high oil pressure is
applied on the valve of a large size power steering when a steering
wheel is turned around. In order to turn the steering wheel smooth
when such a high oil pressure is applied, it is desirable that a
change in a sliding torque is small against a large change in oil
pressure.
[0108] The seal ring of the present invention can be used on such a
large power steering. When the sliding cycle is applied on the seal
ring under the above-mentioned Condition 2, breakage of the seal
ring does not occur at the 200,000th cycle, the sliding torque
within the period of 200,000 cycles without the period of initial
unstable sliding torque is not less than 75%, preferably not less
than 80% of the maximum sliding torque in that period of 200,000
cycles, and during the period of 200,000 cycles without the period
of initial unstable sliding torque, a ratio Tmax15/Tmax12 of the
maximum sliding torque Tmax15 at an oil pressure of 15 MPa to the
maximum sliding torque Tmax12 at an oil pressure of 12 MPa is less
than 1.5, preferably not more than 1.3.
[0109] The meaning of "without the period of initial unstable
sliding torque" is that in the sliding test under a high pressure,
until about 50,000 cycles are reached from starting of the sliding,
the sliding torque does not become stable and sometimes the sliding
torque increases drastically and therefore such an initial unstable
sliding torque is excluded.
[0110] Examples of devices on which the seal ring of the present
invention is used are a hydraulic power steering device, automatic
transmission, engine piston ring and shock absorber for automobiles
and a hydraulic cylinder for industrial machinery. Among them, the
seal ring is suitable for a valve device of a power steering of
automobiles which is particularly required to have characteristics
such as a small resistance at sliding, a less abrasion of the
opposite material, a small deformation of the seal ring under a
high pressure (not less than 8 MPa), and a less leakage of oil even
in case of the use for a long period of time.
[0111] Further the seal ring which is small in a change of a
sliding torque can be provided for a valve device of a large power
steering of large cars (truck, bus, trailer, etc.) though there
have been no seal rings for the large cars having stable sliding
characteristics even under a high pressure.
[0112] Also the seal ring of the present invention is suitable as a
seal ring for an automatic transmission and shock absorber in which
importance is attached to safety and durability is required.
[0113] Namely, the present invention can provide the seal ring for
an automatic transmission in which when a rotating slide is applied
on the seal ring under the above-mentioned Condition 3, breakage of
the seal ring does not occur in 500 hours and the abraded depth of
the opposite material 500 hours after applying the rotating slide
is not more than 10 .mu.m, preferably not more than 5 .mu.m.
[0114] Further the present invention can provide the seal ring for
a shock absorber in which when the reciprocating slide strokes are
applied on the seal ring under the above-mentioned Condition 4,
breakage of the seal ring does not occur at the 5,000,000th stroke,
the maximum slide resistance Fmax within the period of 5,000,000
strokes without the period of initial unstable slide resistance is
less than 1.5 times, preferably not more than 1.3 times the minimum
slide resistance Fmin during that period of 5,000,000 strokes, and
an amount of oil leakage after 5,000,000 strokes is not more than
15 ml, preferably not more than 10 ml.
[0115] The present invention is then explained by means of
examples, but is not limited to them.
EXAMPLE 1
[0116] The resin powder for molding was prepared by pre-mixing 80
parts by weight of a PTFE powder (average particle size: 30 .mu.m)
modified with 1% by weight of perfluoro(propyl vinyl ether), 15
parts by weight of a heat resistant aromatic polyoxybenzoyl ester
resin powder (SUMICA SUPER available from Sumitomo Chemical
Company, Limited, average particle size: 20 .mu.m) and 5 parts by
weight of a natural graphite (CPB-3000 available from Chuetsu
Kokuen Kabushiki Kaisha, average particle size: 9 .mu.m) and then
granulating the mixture.
[0117] The obtained resin powder for molding was subjected to
compression molding to obtain a seal ring for testing (a ring of
inner diameter: 33.4 mm, outer diameter: 36.4 mm, height: 1.88 mm).
The seal ring for testing was subjected to testing for durability
under the above-mentioned Condition 1. The results are shown in
Table 1.
[0118] Test Method
[0119] Test equipment: Test equipment for evaluating durability of
a seal ring which conforms with a rack & pinion type power
steering device
[0120] Oil pressure: 12 MPa
[0121] Oil temperature: 120.degree. C.
[0122] Kind of oil: Power steering fluid (RODEO PSF available from
Nippon Mitsubishi Oil Corporation)
[0123] Sliding cycle: One cycle consists of a normal rotation at 95
rpm for 2 seconds and a reverse rotation at 95 rpm for 2
seconds
[0124] Opposite material: Aluminum die cast ADC12 (JIS H5302)
[0125] Seal ring-mounting material: Carbon steel S45C (JIS
G4051)
[0126] Seal ring: 36.4 mm of outer diameter, 1.5 mm of width, 1.88
mm of height
[0127] Evaluation of Properties
[0128] (Life of seal ring)
[0129] The number of sliding cycles where there occurs breakage of
the seal ring (oil leakage) is assumed to be a life of the seal
ring. The test is suspended when the breakage of the seal ring does
not occur at the 200,000th cycle.
[0130] (Change in sliding torque)
[0131] A rotation torque is recorded when two seal rings which seal
oil are rotating at 95 rpm (2 seconds). A change in a rotation
torque during the period of time from an end of an initial drastic
increase of the torque (7,000 to 25,000 cycles) to 200,000th cycle
is assumed to be a change in a sliding torque.
[0132] The results of measurement are shown in the graph (FIG. 7)
in which the abscissa represents the sliding cycle and the ordinate
represents the sliding torque (N.multidot.m).
[0133] Further the maximum sliding torque Tmax and the minimum
sliding torque Tmin during the period of time of from the 10,000th
cycle to the 200,000th cycle are determined, and a maximum change
in the sliding torque is represented by (Tmin/Tmax).times.100
(%).
[0134] (Maximum abraded depth of opposite material)
[0135] The maximum depth (.mu.m) at the abraded portion
(corresponding to the concave portion 6 in FIG. 4) of the opposite
material (aluminum die cast) is measured when breakage of the seal
ring occurs or when the test is suspended at the 200,000th cycle,
by using a surface roughness meter (SURFTEST SV-600 available from
Mitsutoyo Kabushiki Kaisha).
[0136] (Amount of extrusion of seal ring)
[0137] A length (mm) of an extruded portion (corresponding to an
extruded portion 5 in FIGS. 2 and 3 ) of the seal ring is measured
when the test is suspended at the 200,000th cycle. The seal rings
broken (or subject to oil leak) during the test are excluded.
[0138] (Final shape of cross-section)
[0139] When the breakage of the seal ring (oil leak) occurs or when
the test is suspended at the 200,000th cycle, the seal ring is cut
and a shape of its cross-section is evaluated.
EXAMPLES 2 to 3
[0140] The seal rings of the present invention were produced by
molding in the same manner as in Example 1 except that the amounts
of the heat resistant aromatic polyoxybenzoyl ester resin powder
and graphite powder were changed as shown in Table 1, and the
durability of the seal rings was evaluated in the same manner as in
Example 1. The results are shown in Table 1 and FIGS. 8 and 9
(graphs showing a change in a sliding torque).
Comparative Examples 1 to 4
[0141] The seal rings for comparison were produced by granulating
and molding in the same manner as in Example 1 except that the
fillers shown in Table 1 were used, and the durability of the seal
rings was evaluated in the same manner as in Example 1. The results
are shown in Table 1 and FIGS. 10 to 13 (graphs showing a change in
a sliding torque).
[0142] Abbreviations of the fillers shown in Table 1 (the same in
Tables 2 to 4) are as follows.
[0143] POB: Heat resistant aromatic polyoxybenzoyl ester resin
powder (SUMICA SUPER available from Sumitomo Chemical Company,
Limited, average particle size: 20 .mu.m)
[0144] GR: Natural graphite powder (CPB-3000 available from Chuetsu
Kokuen Kabushiki Kaisha, average particle size: 9 .mu.m)
[0145] CF: Carbon fiber (M2006S available from Kabushiki Kaisha
Kureha, average fiber diameter: 15 .mu.m, average fiber length: 100
.mu.m)
[0146] GRA: Artificial graphite powder (EG-1C available from Nippon
Carbon Kabushiki Kaisha, average particle size: 35 .mu.m)
[0147] BZ: Bronze powder (SD-200 available from Fukuda Kinzoku
Kabushiki Kaisha, average particle size: 20 .mu.m)
[0148] PI: Polyimide powder (KELIMIDE 1050 available from Asahi
Chiba Kabushiki Kaisha, average particle size: 20 .mu.m)
1TABLE 1 Ex. 1 Ex. 2 Ex. 3 Seal ring PTFE powder 80 80 90 Filler
POB 15 10 5 GR 5 5 5 CF GRA BZ PI Durability Life of seal ring
200,000 200,000 200,000 cycles cycles cycles (suspended)
(suspended) (suspended) Change in sliding torque Maximum sliding
torque 1.9 2.1 1.9 Tmax (N .multidot. m) Minimum sliding torque 1.6
1.8 1.6 Tmin (N .multidot. m) (Tmin/Tmax) .times. 100 (%) 84 86 84
Maximum abraded depth of 3.7 5.6 6.6 opposite material (.mu.m)
Amount of extruded portion 0.4 0.3 0.4 of seal ring (mm) Com. Com.
Com. Com. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Seal ring PTFE powder 80 89 60 83
Filler POB 15 GR CF 5 4 10 5 GRA 7 BZ 30 PI 12 Durability Life of
seal ring 200,000 36,800 62,700 56,50 cycles (broken) (broken)
(broken) (sus- pended) Change in sliding torque Maximum sliding
torque 2.5 2.7 3.7 2.4 Tmax (N .multidot. m) Minimum sliding torque
1.5 1.9 1.7 1.7 Tmin (N .multidot. m) (Tmin/Tmax) .times. 100 (%)
60 70 46 71 Maximum abraded depth 10.4 37.0 38.5 37.5 of opposite
material (.mu.m) Amount of extruded 2.1 broken broken broken
portion of seal ring (mm)
EXAMPLE 4
[0149] A life of seal ring, a change in a sliding torque (same oil
pressure), a maximum sliding torque (Tmax), a minimum sliding
torque (Tmin) and Tmin/Tmax.times.100 (%) were measured in the same
manner as in Example 1 by applying oil pressures of 12 MPa and 15
MPa on the seal ring produced in Example 3 (90 parts of PTFE
powder+5 parts of POB+5 parts of natural graphite) under the
above-mentioned test Condition 2 (opposite material: carbon steel
STKM13 (JIS G3445) was used). Further a ratio (Tmax15/Tmax12) of a
maximum sliding torque (Tmax15) at an oil pressure of 15 MPa to a
maximum sliding torque (Tmax12) at an oil pressure of 12 MPa was
calculated.
[0150] The results are shown in Table 2 and FIG. 14 (graph showing
a change in a sliding torque).
Comparative Examples 5 to 7
[0151] The seal rings were produced by using the components shown
in Table 2, and a life of seal ring, a change in a sliding torque
(same oil pressure), a maximum sliding torque (Tmax), a minimum
sliding torque (Tmin) and Tmin/Tmax.times.100 (%) were measured in
the same manner as in Example 4 at oil pressures of 12 MPa and 15
MPa under Condition 2. Further a ratio (Tmax15/Tmax12) of a maximum
sliding torque (Tmax15) at an oil pressure of 15 MPa to a maximum
sliding torque (Tmax12) at an oil pressure of 12 MPa was
calculated.
[0152] The results are shown in Table 2 and FIGS. 15 to 17 (graphs
showing a change in a sliding torque).
2 TABLE 2 Ex. 4 Com. Ex. 5 Oil pressure (MPa) Oil pressure (MPa) 12
15 12 15 Seal ring PTFE powder 90 90 80 80 Filler POB 5 5 15 15 GR
5 5 CF 5 5 GRA BZ Durability Life of seal 200,000 200,000 200,000
200,000 ring cycles cycles cycles cycles (suspended) (suspended)
(suspended) (suspended) Change in sliding torque Maximum 2.0 2.6
3.4 4.8 sliding torque Tmax (N .multidot. m) Minimum 1.7 2.1 3.0
2.6 sliding torque Tmin (N .multidot. m) (Tmin/Tmax) .times. 85 81
88 54 100 (%) Tmax15/ 1.3 1.3 1.4 1.4 Tmax12 Com. Ex. 6 Com. Ex. 7
Oil pressure (MPa) Oil pressure (MPa) 12 15 12 15 Seal ring PTFE
powder 89 89 60 60 Filler POB GR CF 4 4 10 10 GRA 7 7 BZ 30 30
Durability Life of seal 200,000 200,000 200,000 200,000 ring cycles
cycles cycles cycles (suspended) (suspended) (suspended)
(suspended) Change in sliding torque Maximum 5.2 6.2 3.7 6.3
sliding torque Tmax (N .multidot. m) Minimum 3.4 3.8 1.7 5.5
sliding torque Tmin (N .multidot. m) (Tmin/Tmax) .times. 65 61 46
87 100 (%) Tmax15/ 1.2 1.2 1.7 1.7 Tmax12
EXAMPLE 5
[0153] The resin powder for molding was prepared by pre-mixing 80
parts by weight of a PTFE powder (average particle size: 30 .mu.m)
modified with 1% by weight of perfluoro(propyl vinyl ether), 15
parts by weight of a heat resistant aromatic polyoxybenzoyl ester
resin powder (SUMICA SUPER available from Sumitomo Chemical
Company, Limited, average particle size: 20 .mu.m) and 5 parts by
weight of a natural graphite (CPB-3000 available from Chuetsu
Kokuen Kabushiki Kaisha, average particle size: 9 .mu.m) and then
granulating the mixture.
[0154] The obtained resin powder for molding was subjected to
compression molding to obtain a seal ring for testing (The ring had
an inner diameter of 46 mm, an outer diameter of 50 mm and a
thickness of 2 mm and was cut at one portion thereof at an angle of
30 degrees to a tangential line. A gap of the cut portion was 0.1
mm. Refer to FIG. 18.). The seal ring for testing was subjected to
testing for durability under the above-mentioned Condition 3. The
results are shown in Table 3.
[0155] Test Method
[0156] Test equipment: Test equipment for evaluating durability of
a seal ring which conforms with an automatic transmission
device
[0157] Oil pressure: 2 MPa
[0158] Oil temperature: 120.degree. C.
[0159] Kind of oil: Automatic transmission fluid (ATF D4 available
from Nippon Mitsubishi Oil Corporation)
[0160] Number of rotations 8,000 rpm
[0161] Opposite material: Aluminum die cast ADC12 (JIS H5302)
[0162] Seal ring-mounting material: Cast iron FC205 (JIS G5501)
[0163] Seal ring: 50 mm of outer diameter, 2 mm of width, 2 mm of
height
[0164] Evaluation of Properties
[0165] (Life of seal ring)
[0166] The sliding cycle when breakage of the seal ring (oil
leakage) occurs is assumed to be a life of the seal ring. The test
is suspended when the breakage of the seal ring does not occur in
500 hours.
[0167] (Maximum abraded depth of opposite material)
[0168] The maximum depth (.mu.m) at the abraded portion
(corresponding to the concave portion 6 in FIG. 4) of the opposite
material (aluminum die cast) is measured at the time when breakage
of the seal ring occurs or when the test is suspended in 500 hours,
by using a surface roughness meter (SURFTEST SV-600 available from
Mitsutoyo Kabushiki Kaisha).
EXAMPLES 6 to 7
[0169] The seal rings of the present invention were produced by
molding in the same manner as in Example 5 except that the amounts
of the heat resistant aromatic polyoxybenzoyl ester resin powder
and graphite powder were changed as shown in Table 3, and the
durability of the seal rings was evaluated in the same manner as in
Example 5. The results are shown in Table 3.
Comparative Examples 8 to 11
[0170] The seal rings for comparison were produced by granulating
and molding in the same manner as in Example 5 except that the
fillers shown in Table 3 were used, and the durability of the seal
rings was evaluated in the same manner as in Example 5. The results
are shown in Table 3.
3TABLE 3 Ex. 5 Ex. 6 Ex. 7 Seal ring PTFE powder 80 85 90 Filler
POB 15 10 5 GR 5 5 5 CF GRA BZ PI Durability Life of seal ring
(hour) 500 500 500 (suspended) (suspended) (suspended) Maximum
abraded depth of 3.1 3.8 3.8 opposite material (.mu.m) Com. Ex. 8
Com. Ex. 9 Com. Ex. 10 Com. Ex. 11 Seal ring PTFE powder 80 89 60
83 Filler POB 15 GR CF 5 4 10 5 GRA 7 BZ 30 PI 12 Durability Life
of seal 500 500 250 500 ring (hour) (suspended) (suspended)
(broken) (suspended) Maximum 11.5 25.5 40.5 15.5 abraded depth of
opposite material (.mu.m)
EXAMPLE 8
[0171] The resin powder for molding was prepared by pre-mixing, by
usual method, 80 parts by weight of a PTFE powder (average particle
size: 30 .mu.m) modified with 1% by weight of perfluoro(propyl
vinyl ether), 15 parts by weight of a heat resistant aromatic
polyoxybenzoyl ester resin powder (SUMICA SUPER available from
Sumitomo Chemical Company, Limited, average particle size: 20
.mu.m) and 5 parts by weight of a natural graphite (CPB-3000
available from Chuetsu Kokuen Kabushiki Kaisha, average particle
size: 9 .mu.m) and then granulating the mixture.
[0172] The obtained resin powder for molding was subjected to
compression molding to obtain a seal ring for testing (a ring of
inner diameter: 13.7 mm, outer diameter: 28.5 mm, thickness: 0.8
mm). The seal ring for testing was subjected to testing for
durability under the above-mentioned Condition 4. The results are
shown in Table 4.
[0173] Test Method
[0174] Test equipment: Test equipment for evaluating durability of
a seal ring which conforms with a shock absorber device
[0175] Inner diameter of piston: 25 mm
[0176] Oil pressure: 10 MPa
[0177] Oil temperature: 100.degree. C.
[0178] Kind of oil: Shock absorber oil
[0179] Length of stroke: 60 mm. One reciprocation is assumed to be
one stroke.
[0180] Vibration frequency to be applied: 3 Hz
[0181] Opposite material: Carbon steel S45C (JIS H4051)
[0182] Seal ring-mounting material: Cast iron FC250 (JIS G5501)
[0183] Seal ring: 28.5 mm of outer diameter, 7.4 mm of width, 0.8
mm of height (diameter of piston: 25 mm)
[0184] Evaluation of Properties
[0185] (Life of seal ring)
[0186] The number of sliding strokes when breakage of the seal ring
occurs (in a state that oil leaks and an oil pressure cannot be
maintained) is assumed to be a life of seal ring. The test is
suspended when breakage of the seal ring does not occur at the
5,000,000th stroke.
[0187] (Change in sliding resistance)
[0188] Among friction resistances generated when the seal ring
wound on the piston and the inner surface of the cylinder make a
relative reciprocating motion, a maximum resistance in each stroke
is assumed to be a sliding resistance in that stroke. A maximum
sliding resistance Fmax and a minimum sliding resistance Fmin are
measured during the interval between an end of an initial drastic
increase of the sliding resistance (There is a case where the end
of the increase is detected by the 500,000th stroke) and the
5,000,000th stroke (or breakage of the seal ring), and a maximum
change in the sliding resistance is represented by
(Fmin/Fmax).times.100 (%).
[0189] (Amount of oil leak)
[0190] After completion of 5,000,000 strokes, oil leaked from an
oil chamber is collected and an amount thereof is measured with a
measuring cylinder.
EXAMPLES 9 to 10
[0191] The seal ring of the present invention was produced by
molding in the same manner as in Example 8 except that the amounts
of the heat resistant aromatic polyoxybenzoyl ester resin powder
and graphite powder were changed as shown in Table 4, and the
durability of the seal ring was evaluated in the same manner as in
Example 8. The results are shown in Table 4.
Comparative Examples 12 to 15
[0192] The seal rings for comparison were produced by granulating
and molding in the same manner as in Example 8 except that the
fillers shown in Table 4 were used, and the durability of the seal
rings was evaluated in the same manner as in Example 8. The results
are shown in Table 4.
4TABLE 4 Ex. 8 Ex. 9 Ex. 10 Seal ring PTFE powder 80 85 90 Filler
POB 15 10 5 GR 5 5 5 CF GRA BZ PI Durability Life of seal ring 500
500 500 (.times.10 .sup.4 strokes) (suspended) (suspended)
(suspended) Maximum sliding resistance 80 84 81 Fmax (N .multidot.
m) Minimum sliding resistance 62 60 62 Fmin (N .multidot. m)
(Fmin/Fmax) .times. 100 (%) 1.3 1.4 1.3 Amount of oil leak (ml) 9 8
8 Com. Ex. 12 Com. Ex. 13 Com. Ex. 14 Com. Ex. 15 Seal ring PTFE
powder 80 89 60 83 Filler POB 15 GR CF 5 4 10 5 GRA 7 BZ 30 PI 12
Durability Life of seal 500 500 250 500 (.times. 10.sup.4 strokes)
(suspended) (suspended) (broken) (suspended) Maximum 110 120 170
115 sliding resistance Fmax (N .multidot. m) Minimum 65 67 85 64
sliding resistance Fmin (N .multidot. m) (Fmin/Fmax) .times. 1.7
1.8 2.0 1.8 100 (%) Amount of oil 15 24 200 21 leak (ml)
[0193] In the seal ring of the present invention, a stable sealing
effect can be obtained for a long period of time since a
deformation of the seal ring is small even under a high pressure
and an abrasion of an opposite material can be inhibited even if
the opposite material is a soft metal. Further since a frictional
force is small and a change in a sliding torque, particularly a
change in a sliding torque at high oil pressure is small,
operability and response of a valve device of a power steering,
particularly a power steering of large cars can be enhanced
markedly.
[0194] Also the seal ring of the present invention can exhibit
excellent performance which has not been obtained so far, as a seal
ring for an automatic transmission which slides at high revolutions
and as a seal ring for a shock absorber which requires a sealing
property under reciprocating sliding environment.
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